FORS_TRACE_FLAT(7)

🦋 FORS_TRACE_FLAT(7) 🦋

okay bestie come CLOSE, this is the section 7 man page for fors_trace_flat from the fors recipes collection and it's lowkey a whole journey 💖. it's about figuring out how the spectral curvature behaves in your MOS/MXU flat fields. strap in, we're doing science.

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✨ NAME ✨

fors_trace_flat — Determine spectral curvature model 👑

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🎀 SYNOPSIS 🎀

esorex fors_trace_flat [OPTIONS] FILE.sof

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💅 DESCRIPTION 💅

okay so this recipe's whole job is to trace the edges of your MOS/MXU flat field slit spectra and then work out the spectral curvature solution. the input master flat field image — which is the product of the recipe fors_flat — is expected to be oriented with the dispersion direction going horizontal, and the red wavelengths chillin' on the right side. 🔥

the input slits location table? that should be the product of the recipe fors_detect_spectra. no substitutions, bestie.

here's the actual pipeline of what happens, step by step, no cap:

• the input master flat image gets shifted one pixel down and then subtracted from the original image. what you're left with is a vertical gradient map. 😌
• next, the negative values get forced positive, so now you've got an absolute gradient map.
• that map goes through a horizontal median filter.
• after that, the gradient peaks get traced, starting from the slits positions listed in the input slits location table.
• the number of pixels to the left and to the right of the reference pixel is trivially derived from the specified spectral range and the spectral dispersion.

the output spectral curvature table contains the coefficients of the polynomial fitting of the found traces. meanwhile the output trace table contains the traced spectral edges positions in CCD (Y) coordinates for each spectrum, plus their comparison with their modeling. a spatial map is also created, where each CCD pixel gets assigned the value of the spatial coordinate along the slit (in pixel). for more deets please refer to the FORS Pipeline User´s Manual. 📖

ngl, specifying an input GRISM_TABLE will set some of the recipe configuration parameters to default values valid for a particular grism. so like, it changes stuff behind your back (helpfully).

again, see the pipeline manual for more details. i'm not gonna lie to you, the manual is the main character here.

in the table below, the MXU acronym can alternatively be read as MOS. iykyk 🫶

Input files:

• DO category: MASTER_SCREEN_FLAT_MXU — Type: Calib — Explanation: Master flat frame — Required: Y
• DO category: SLIT_LOCATION_DETECT_MXU — Type: Calib — Explanation: Slits location — Required: Y
• DO category: GRISM_TABLE — Type: Calib — Explanation: Grism table — Required: .

Output files:

• DO category: CURV_TRACES_MXU — Data type: FITS table — Explanation: Flat field tracings
• DO category: CURV_COEFF_MXU — Data type: FITS table — Explanation: Spectral curvature table
• DO category: SPATIAL_MAP_MXU — Data type: FITS image — Explanation: Map of spatial coordinate

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🌈 OPTIONS 🌈

• --dispersion <float> — Expected spectral dispersion (Angstrom/pixel) (float; default: 0.0). the full name of this option for the EsoRex configuration file is fors.fors_trace_flat.dispersion [default = 0.0].
• --startwavelength <float> — Start wavelength in spectral extraction (float; default: 0.0). the full name of this option for the EsoRex configuration file is fors.fors_trace_flat.startwavelength [default = 0.0].
• --endwavelength <float> — End wavelength in spectral extraction (float; default: 0.0). the full name of this option for the EsoRex configuration file is fors.fors_trace_flat.endwavelength [default = 0.0].
• --cdegree <int> — Degree of spectral curvature polynomial (int; default: 0). the full name of this option for the EsoRex configuration file is fors.fors_trace_flat.cdegree [default = 0].
• --cmode <int> — Interpolation mode of curvature solution applicable to MOS-like data (0 = no interpolation, 1 = fill gaps, 2 = global model) (int; default: 1). the full name of this option for the EsoRex configuration file is fors.fors_trace_flat.cmode [default = 1].

note that it is possible to create a configuration file containing these options, along with suitable default values. please refer to the details provided by the esorex --help command. 💖

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🔭 SEE ALSO 🔭

the full documentation for the fors pipeline can be downloaded as a PDF file using the following URL:

ftp://ftp.eso.org/pub/dfs/pipelines/fors/fors-pipeline-manual-4.9.pdf

an overview over the existing ESO pipelines can be found on the web page https://www.eso.org/sci/software/pipelines/. 🌸

basic documentation about the EsoRex program can be found at the esorex (1) man page.

it is possible to call the pipelines from python using the python-cpl package. see https://packages.python.org/python-cpl/index.html for further information. 🐍✨

the other recipes of the fors pipeline are fors_align_sky(7), fors_align_sky_lss(7), fors_bias(7), fors_calib(7), fors_config(7), fors_dark(7), fors_detect_objects(7), fors_detect_spectra(7), fors_extract(7), fors_extract_objects(7), fors_extract_slits(7), fors_flatfield(7), fors_img_science(7), fors_img_screen_flat(7), fors_img_sky_flat(7), fors_normalise_flat(7), fors_photometry(7), fors_pmos_calib(7), fors_pmos_extract(7), fors_pmos_science(7), fors_remove_bias(7), fors_resample(7), fors_science(7), fors_spec_mflat(7), fors_subtract_sky(7), fors_subtract_sky_lss(7), fors_sumflux(7), fors_wave_calib(7), fors_wave_calib_lss(7), fors_zeropoint(7) — the whole friend group, literally. 👑

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⭐ VERSION ⭐

fors_trace_flat 5.5.7

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🫶 AUTHOR 🫶

Carlo Izzo <usd-help@eso.org> — iconic of them, fr fr.

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💀 BUG REPORTS 💀

please report any problems to usd-help@eso.org. alternatively, you may send a report to the ESO User Support Department <usd-help@eso.org>. don't be shy, they want to hear it. 🙈

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👑 LICENSE 👑

this file is currently part of the FORS Instrument Pipeline Copyright (C) 2002-2010 European Southern Observatory.

this program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

this program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. see the GNU General Public License for more details.

you should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

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and that's the whole page bestie 🎀 — this was fors_trace_flat version 5.5.7 (the FORS_TRACE_FLAT(7) of it all), dated in the manual footer as 5.5.7. go trace some spectra, you absolute main character. 💜